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- Western Afghanistan has been struck by four major earthquakes in just over a week.
- A researcher with the US Geological Survey said these earthquakes are "unprecedented."
- Unsure when they'll end, Afghan residents are living in tents to avoid collapsing buildings.
Western Afghanistan was struck by yet another powerful earthquake on Sunday, its fourth in just over a week.
Sunday's earthquakes came in at 6.3 and 5.4 magnitudes, with the epicenter just 20 miles outside Herat City, The New York Times reported.
About 1,300 people were killed by the initial 6.3 magnitude earthquake on October 7. Another 1,700 were injured. A fourth major earthquake struck the region on October 11.
Over the last week, Herat Province residents — who are unsure when the tremors will cease — have fled the region or moved into tents to avoid collapsing buildings.
This series of major earthquakes is unprecedented for the region, according to William Barnhart, assistant coordinator for the US Geological Survey Earthquake Hazards Program.
"There's very little precedent for a sequence like this where you have four earthquakes of the same magnitude in a week, and even less precedence in this part of Afghanistan where, to the best of my knowledge, there's just no history of damage and earthquakes in and around Herat," Barnhart told Insider.
That makes these quakes especially dangerous for residents of Herat. Buildings and infrastructure tend to be vulnerable in regions that aren't prone to earthquakes, Barnhart said.
Earthquakes of this frequency and size following an initial 6.3-magnitude quake are rare almost anywhere in the world.
"I've been looking through statistics and I haven't found instances of this except for cases in volcanically active regions or in aftershock sequences of much bigger earthquakes," Barnhart said. "But neither of those scenarios apply to this ongoing earthquake sequence."
While Barnhart said it's unlikely the region will experience yet another 6.3-magnitude earthquake, he said he can't know for sure.
"We have no way of predicting what will happen," Barnhart said. "Hopefully, this is the end of this sequence, but it is possible that there could be more earthquakes of this magnitude or perhaps even larger."